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Strictly speaking, when we measure whether the indoor temperature is comfortable, we should take the temperature measured by the wet bulb thermometer at the height of 1.5m from the ground in the center of the room as the judgment basis, and simulate the temperature that people feel indoors through the wet body surface by this method, which is generally called somatosensory temperature. For the radiator of convective heat transfer, only the indoor air is heated first, and then the air transfers heat to the human body, making the user feel warm. Therefore, the heating effect of the radiator, that is, the indoor temperature field spread by the radiator, depends not only on its own material and structure, but also on the indoor wind field and pressure field. Extremely speaking, if the heat sink is placed in a vacuum environment, even if its surface temperature reaches 85℃, it will not produce the effect of convective heat dissipation at all. Therefore, for the heat sink that needs to be attached to the maintenance structure, its installation position is a problem that needs attention.
According to the recommended order, the common installation positions of heat sinks are under the window, by the window, behind the door and inside the wall. The following are some explanations.
For rooms with small area but high requirements for heating comfort like bedrooms, it is generally recommended to install the radiator under the window for two reasons:
1. Improve the heating response speed
The heat exchange between heat sink surface and air, and between air and air belongs to convection heat exchange. Common sense and theoretical knowledge tell us that in the process of convective heat transfer, the greater the temperature difference between the heated object and the heated object, the higher the air velocity and the greater the thermal conductivity. Because the thermal conductivity of the doors and windows of the building is very high (easy to dissipate heat), a certain amount of cold air will penetrate into the gap, so the temperature near the outer window is the lowest in the room. Therefore, when the radiator is placed under the window, the temperature difference is the largest, and the airflow speed is also the largest, so that the radiator emits the most heat to the room in unit time, which can quickly increase the indoor temperature.
2. Equilibrium room temperature
Indoor cold air mainly comes from doors and windows. Because of the high density of low-temperature air, the cold air entering the room will wander on the ground, which just conflicts with the hot and cold temperature fields under people's preference. Therefore, isolating or heating these cold air will greatly improve the heating comfort. The following figure shows some typical indoor heating temperature fields (from left to right: the radiator is installed under the window, the radiator is installed under the window with the same width as the window, and the floor heating and radiator are installed on the inner wall).
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As can be seen from the figure, due to the infiltration of cold air, all temperature fields will have a temperature drop zone near the ground. Among them, the radiator with the same width as the window heats the cold air entering the window gap, which minimizes the influence of cold air. However, the calculated radiator length is generally less than the width of the window, and the radiator with the same width as the window will increase the cost and occupy the indoor space, so it is rarely used.
Comparing the temperature field between radiator heating under the window and interior wall heating, it is found that installing radiator under the window can better balance the indoor temperature. In the practical application process, we also found that due to the intervention of cold air, the hot air above the heat sink is cooled and increased, which can weaken the baking feeling of users standing next to the heat sink on the premise of ensuring heat dissipation.
Pay attention to some details when installing the heat sink under the window. 1. The radiator is off the ground 10cm+ to ensure the smooth airflow at the lower part. It is suggested that the upper part of the radiator is lower than the window sill 10cm+ to form a hot air curtain and effectively mix cold air. Secondly, be sure to avoid the radiator being covered by curtains, which will seriously affect the heating effect, as shown in the following figure:
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For rooms with floor-to-ceiling windows, such as living rooms, it is impossible to install heat sinks under the windows. What position should we choose? In fact, this situation is more complicated, although it is recommended to consider windows, doors and interior walls in turn. But in practical application, these positions are often occupied by all kinds of furniture. In the living room, we often need to use 900mm high fins to avoid overcrowding on the wall. You should know that the fins under the window only need to be 600 mm high, and the layout of the living room also has an impact on heating. Placing radiators by the window can really heat cold air to a certain extent, but sometimes these positions are too close to the bed, which will make users feel obvious temperature gradient and obviously uncomfortable. Putting fins behind the door can greatly save the length of the pipeline, and doors and windows are similar areas where cold air flows strongly, but the size of the door frame and the aesthetic preferences of users have great restrictions on this way. Sometimes, due to various factors, the installer has to put the heat sink on the inner wall facing the window. As can be seen from the figure 1, generally speaking, this is the most inappropriate scheme, but in fact, if it is set properly, it can achieve good results. For example, by virtue of the area advantage of the inner wall, placing two sets of relatively short fins diagonally instead of the original set of fins can generally achieve better heat dissipation effect.